Cumulative (time-integrated) gwIMF (TIgwIMF) for all stars ever formed (thick solid line) and the gwIMF for each 10 Myr star formation epoch (thin solid lines, evolving from the top to the bottom as time progresses) of the best-fit IGIMF-R14 model, compared with the canonical IMF and the Salpeter IMF. We note that the gwIMF for the first epoch (the highest thin gwIMF line) has a significantly higher maximum stellar mass limit than the second epoch. This is only because the initial metallicity was assumed to be Z = 0.02 × 10⁻⁷ and because the 10 Myr time step is unresolved.